docs: def extract_shared_optional(bel_resource, definition_header: str = 'Namespace'):
      """Get the optional annotations shared by BEL namespace and annotation resource documents.
  
      :param dict bel_resource: A configuration dictionary representing a BEL resource
      :param definition_header: ``Namespace`` or ``AnnotationDefinition``
      :rtype: dict
      """
      shared_mapping = {
          'description': (definition_header, 'DescriptionString'),
          'version': (definition_header, 'VersionString'),
          'author': ('Author', 'NameString'),
          'license': ('Author', 'CopyrightString'),
          'contact': ('Author', 'ContactInfoString'),
          'citation': ('Citation', 'NameString'),
          'citation_description': ('Citation', 'DescriptionString'),
          'citation_version': ('Citation', 'PublishedVersionString'),
          'citation_url': ('Citation', 'ReferenceURL'),
      }
  
      result = {}
  
      update_insert_values(bel_resource, shared_mapping, result)
  
      if 'PublishedDate' in bel_resource.get('Citation', {}):
          result['citation_published'] = parse_datetime(bel_resource['Citation']['PublishedDate'])
  
      return result